1. Field of the Invention
The present invention relates to an apparatus and method for image/voice transmission used in a communication field.
2. Description of the Related Art
In a conventional image/voice transmission apparatus, data error decision is performed only on codes after data multiplexing and when code errors occur in either an image or voice, both the image and voice are treated as having errors.
FIG. 1 is a block diagram showing a configuration of a conventional image/voice transmission apparatus. The apparatus on the transmitting side comprises voice coding section 11 that encodes voice data, image coding section 12 that encodes image data, multiplexing section 13 that multiplexes coded voice data and image data, error decision bit addition section 14 that adds an error decision bit to the multiplexed data and transmission section 15 that sends the multiplexed data with the bit added to the apparatus on the receiving side.
On the other hand, the apparatus on the receiving side comprises reception section 16 that receives the data sent from the apparatus on the transmitting side, reception error decision section 17 that performs reception error decision on the received multiplexed data, separation section 18 that separates the data after error decision into voice data and image data, voice decoding section 19 that decodes the separated voice data and image decoding section 20 that decodes the separated image data.
In the apparatus on the transmitting side of the conventional image/voice transmission apparatus, when voice or an image is input, voice coding section 11 generates a voice code (voice data) and image coding section 12 generates an image code (image data). Then, multiplexing section 13 multiplexes the voice data and image data. Error decision bit addition section 14 adds an error decision bit to the multiplexed data. Then, the data with the bit added is sent from transmission section 15 to the apparatus on the receiving side.
In the apparatus on the receiving side, reception section 16 receives the multiplexed data with the error decision bit added and reception error decision section 17 performs error decision on the multiplexed data. When the data includes an error, the code string within the error decision range is normally discarded and a retransmission request is separately sent to the apparatus on the transmitting side. When the data includes no error, separation section 18 separates the multiplexed data into voice data and image data codes. Then, the separated voice data is decoded by voice decoding section 19 and output, and the separated image data is decoded by image decoding section 20 and output.
Since the above conventional image/voice transmission apparatus performs error decision on the reception data made up of multiplexed image data and voice data, even if the voice data has no error, when the image data includes an error, the multiplexed data is decided to have an error and this data is discarded. This results in a problem that decoding of voice data whose continuity is important from an auditory standpoint is interrupted.
It is an object of the present invention to provide an apparatus and method for image/voice transmission capable of effectively using voice data when multiplexed image data contains an error and voice data contains no error, and correctly and uninterruptedly decoding voice data.
A theme of the present invention is to add an error decision bit to image data and voice data independently before multiplexing these data, take advantage of the fact that error decision is performed on the reception data after the image and voice are separated and even if the code of the multiplexed image section contains an error, use the voice code data as valid data in the case where the voice section data contains no error.
Thus, even if the code of the multiplexed image section contains an error, in the case where the voice section data contains no error, it is possible to use the voice code data as valid data. Thus, decoding of voice whose continuity is important from an auditory standpoint can be performed uninterruptedly.